Spark plug



1960 J. J. HEIGL ETAL 2,947,900

SPARK PLUG Filed June 28, 1957 3 Sheets-Sheet l John J. Heigl Albert .J. Blackwood By Attorney lnvenrors J. J. HElGL ETAL SPARK PLUG 3 Sheets-Sheet a B Attorney FIG Aug. 2, 1960 Filed June 28, 1957 7 Patented Aug. 2, I960 SPARK PLUG John J. Heigl, Short Hills, Albert J. Blackwood,

Westfield, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed June 28, 1957, Ser. No.668,657 7 Claims. (Cl. 313-132 compress the fuel charge within the port is less so that This invention relates to spark plugs for internal com- I bustion engines and more particularly relates to a modified spark plug which provides supplementary ignition for internal combustion engines when the spark plug or plugs misfire or fail to fire.

During high speed operation of spark ignition engines, erratic combustion is. often encountered. Especially is this true with modern high compression ratio engines and particularly where certain deposits build up on'the spark plug surfaces which result in and cause misfiring under certain critical conditions of operation. The spark plugs do not fire properly when subjected to temperature-pressuredeposit conditions at the high engine speed. In some cases at speeds of above about 60 miles per hour, spark plug misfiring may approach 50 percent of the fin'ng opportunity.

The spark plug of the present invention is useful for internal combustion engines such as the two or the four cycle engines and is especially useful for automobile and airplane engines, marine engines, etc.

According to the present invention an improved spark plug is provided having supplementary means for igniting the charge or fuel in the combustion chamber of the engine which is independent of the electrical ignition that provides the normal spark or arc. With the present invention the conventional spark plug is modified to have one or more small compression chambers to receive part ofthe charge or fuel from the combustion chamber of the engine to provide supplementary ignition of the charge or fuel during operation of the engine. With the present invention this is done by providing a port or series of ports in' the spark plug which at relatively high engine speeds will retain a burning portion of the combustion mixture from one cycle and then ignite the following cycle charge therewith. At low speed operation, as below about 25 miles per hour for an automobile, the normal arcing of the spark plug works satisfactorily. At the higher speeds, that is above about 35 miles per hour for an automobile, the burning charge from the port or ports sustain combustion. h V

Instead of trapping a portion'of the burning charge in the port or ports and carrying this burning over to the next cycle, the port or ports can function to entrap a portion of the fuel or charge from the combustion chamber of the engine and then have it compressed in the port or ports to its ignition temperature so that the port or parts function as a diesel engine and ignite the charge or fuel by supplementary ignition by compression.

Or the residual hot combustion gases in the port or ports function to add heat to the charge or fuel being compressed into, the port or ports until the compression has reached a pressure suflicient' to ignite the charge.

One or more ports or wells may be incorporated in the spark plug, preferably in the'porcelain section or in the central electrode of the spark'plug. The ports or wells may be provided in the metal shell of the spark plug. When a series of ports or wells are used they are of different sizesso that the ratios of the lengths to di ameters of the wells or ports are suitable for an engine speed range. At the lower speeds, below about 35 miles per'hour'of the automobile, a larger length to diameter ratio is suitable, whereas at the higher speeds, above about 35 miles per hour, smaller ratios of length to diameter are best. At the higher speeds, the temperature in the port area of the plug is higher and the time to a smaller length to diameter ratio will sustain burning of the charge within the port.

Instead of using a plurality of ports in a spark plug, the spark plug can be provided with a single port or well of a certain length to diameter ratio. One set of such spark plugs would be suitable for one speed range. Another'set of spark plugs can be provided with a smaller length to diameter ratio port or well useful for an engine run at higher speeds Other sets of spark plugs using different sized ports'or wells may be used as desired.

In a modification of the invention a spark plug is provided having a hollow cylindrical central or axial electrode which provides a well or port for the spark plug. In this form of the invention, the hollow central electrode still functions as the central electrode. In this modification of the invention the depth of the well or port is adjustable by means of a plunger screwed or otherwise adjustablysecured and mounted in the hollow electrode. Adjustment is from the top of the electrode. By adjusting the screw on the plunger, the compression of the charge or fuel in the port or well can be varied until the desired ignition is obtained in any given installation of the spark plug.

In the drawings:

Fig. 1 represents a partial vertical longitudinal cross section of one form of the invention in which the insulation body is provided with one or more wellsor ports;

Fig. 2 represents a horizontal tranverse cross section 7 taken substantially on line 2-2 of Fig. l;

Fig. 3 represents a horizontal transverse cross section taken substantially on line 3-3 of Fig. 1;

Fig. 4 represents a vertical longitudinal cross section of a half of another form of the invention in which the i well or port is providedin the metal shell of the spark Fig. 5 represents a horizontal transverse cross section taken substantially on line 5-5 of Fig. 4;

' Fig. 6 represents avertical longitudinal cross section taken on another form of the invention in which the central electrode is formed as a hollow cylinder and is provided with means for adjusting the depth of the well or port formed in the lower portion of the central electrode;

' Fig. 7 represents an enlarged detail showing the means for adjusting the and Fig. 8 represents an enlarged detail of another form of the invention using a" hollow central electrode.

Referring now to 'Figs. land 2 of the drawing the reference character 10 designates a conventional spark plug for use in internal combustion engines such as used in automobiles, airplanes, marine engines and the like.

plunger'means in the central electrode;

The conventional spark plug is modified to incorporate supplementaryignition means as will be presently described. The spark plug 10 has a central refractory core or insulation 12 through which passes and is securely held a solid central or axial metal electrode 14. The top of the electrode 14 is threaded to receive a nut 16 for holding a wire (not shown) to conduct high voltage current to electrode 14 at certain selected intervals. The bottom of electrode 14 extends below insulation body 12 as at 18.

The insulation body 12 has an enlarged central portion securely held in metal shell 20 between annular gasket 22 and bevelled seat 24 at the bottom portion of the enlarged central portion of body 12. Metal shell 20 has a hexagonal formed nut portion 26 which is used for screwing the spark plug into place in an engine. The lower portion of the metal shell 20 has an external threaded portion 28 for securing the spark plug in a threaded hole in an internal combustion engine. The lower end of shell 20 has a second electrode 30 which extends toward the bottom 18 ofcentral electrode 14 and is spaced therefrom to form a spark gap to supply the electrical ignition for the compressed charge of gasoline and air in the combustion chamber of the internal combustion engine. Electrode 30 is grounded to the engine.

In present day internal combustion engines where the compression ratios have gone up as high as 8 to l and higher, it has been noticed that at high speeds equivalent to car speeds of about 35 to 100 miles per hour, that there is periodic misfiring of the conventional spark plugs and in some cases continual misfiring of the spark plugs. The following has been observed during a road test consisting of an acceleration from zero to 80 miles per hour: in the :low speed range up to 35 miles per hour there was no misfire of any spark plugs; in the intermediate speed range (35-50 miles per hour) there was a periodic misfire of one or more spark plugs; in the high speed range (50-80 miles per hour), there was a continual misfire of one or more spark plugs. It is during these periods of misfire at intermediate and high speed when the present invention is operative and produces a source of ignition when the spark ignition system misfires. When the spark ignition system is working at the higher speeds, the supplementary or auxiliary ignition system of the present invention is also working.

In some cases and under some conditions, spark plug misfiring (periodic or continual) may approach 50% of the firing opportunity. Some of this may be due to spark plug fouling by fuels and lubricants. The increased compression ratios in engines have added to the problem. It is assumed and necessary that the components of the ignition system (battery, distributor, high tension coil, etc.), are in satisfactory working condition. Defects in the ignition system can in no way be overcome by employing the present invention.

As shown in Fig. 1 the porcelain or insulation body 12 is provided with two wells or ports 32 and 34 in the intermediate portion of the body 12. A third port or well 35 is shown in the lower portion of body 12. Usually only one well or port is necessary but more may be used, if desired. Three wells or ports have been shown to illustrate that these wells or ports may be of different sizes and located in different parts of the spark plug. All wells 32, 34 and 35 are circular in cross section as can be seen in Figs. 2 and 3 and both wells are linear and parallel to central electrode 14. Wells 32 and 34 open into the annular space 36 between metal shell 20 and the bottom portion 38 of insulator body 12. Well or port 35 is in the lower portion of body 12 and opens into the space below the bottom face or surface 39 of porcelain body 12. The face 39 is spaced upwardly from the bottom edge 40 of the screw threaded portion of metal shell 20. Well 35 is arranged on the right in Fig. l to be positioned away from electrode 30 to permit free access of the fuel charge to the well 35 without obstruction by electrode 30.

As can be seen in Fig. 1 the inner or top ends of wells or ports 32, 3'4 and 35 are closed and the lower ends are open so that a charge of fuel, such as gasoline, and air which is compressed in a combustion chamber of the engine will partly enter wells or ports 32, 34 and 35 and at relatively high speeds of the engine, the portion of the combustible mixture of fuel and air in one or all of wells or ports 32, 34 and 35 will be compressed sufficiently to ignite this portion of the combustible mixture and if the electrical ignition fails, this ignited portion of the combustible mixture will ignite the compressed combustible mixture in the combustion chamber. The preferred position of the port or ports is like that shown for port .35 as this is the hottest section of the spark plug being near electrode 14 and near the bottom of the porcelain body 12 and further away from metal shell 20.

The ports or wells 32, 34 and 35 are of different size so that the length to diameter ratio (L/D) is suitable over a speed range. At the lower engine speeds equivalent to car speeds up to about 50 miles per hour,, a larger L/D ratio is suitable while at the higher engine speeds, equivalent to car speeds above about 50 miles per hour, smaller L/D ratios are selected. The port or well length may be between about 2 inches and A; of an inch and the diameter may be between about ,4 and A1 of an inch so that the L/D may vary between about 128 and 0.5. Preferably, the L/D is in the range of from about 5 to 20. The L/D ratios will also vary with compression ratios as well as with operating temperatures.

At the higher engine speeds the combustible mixture of fuel and air from the combustion chamber in the engine is forced into ports 32 and 34 rapid-1y which heats the combustible mixture up faster. In addition some of the residual mixture burning from the previous charge is still in the well or port when a fresh charge of combustible mixture is brought in and this helps to heat up the portion of the combustible mixture in the port or well to bring it up to self-ignition temperature more quickly.

Referring now to Figs. 4 and 5, the same reference characters will be used to designate the same parts. In the modification shown in Figs. 4 and 5, the well or port is provided in the metal shell 20 rather than in the porcelain or insulating body 12. The well or port is shown at '42 as extending upwardly to the left at an angle as shown in Fig. 4 for a short distance after which it joins a vertical channel '44. The channel or port 44 is circular in horizontal cross section and is formed by boring through shell 20. The bottom portion of channel 44 is closed off by plug 46. Port 42 is cylindrical and in the section shown in Fig. 5, channel or port 42 is shown as an ellipse due to the way the section line is taken. The lower end of channel or port 42 opens and communicates space 36 between the bottom portion 38 of the porcelain body 12 and the threaded bottom portion 28 of the shell 20. The L/D ratio for ports 42 and 44 are substantially the same as that given for ports 32, 34 and 35 in Fig. 1. As between the modifications of Figs. 1 and 4, the form of the invention shown in Fig. l is preferred.

Referring now to Figs. 6 and 7, the same reference characters are used to designate similar parts. In this form of the invention the axial electrode is changed and the other electrode attached to metal shell 20 is also changed. As pointed out above, different L/D ratios are needed for different engine speeds and for different compression ratios. With this form of the invention the L/D ratio can be varied and adjusted to get the correct compression in the Well or port for a desired speed range. The central electrode 52 is formed as a hollow vertical cylinder which extends below the porcelain insulating body 12 as at 54. As shown in Fig. 7 the upper inner wall of electrode 52 is threaded for a portion of its length to receive an externally threaded solid cylindrical member 56 having a slot 58 in its upper end for a screw driver or the like. Member 56 is connected to solid connected to threaded member 56and piston or cylinder 60 orit may be connected by ball joints to permit relative movement between member 56 and cylinder 60. The depth or lengthof the port or cavity 63 in central electrode 52 below solid cylinder 60 can be varied by raising or lowering cylinder 60. After the position of the cylinder 60 is established to produce the desired L/D ratio, the screw member and its associated parts are locked in place. However, occasional adjustments may be made, if desired.

In order to prevent heat loss from the top of the central electrode 52, any suitable heat insulationsuch as magnesia may be introduced into the upper end of axial or central electrode 52 as shown at 64. The amount of heat conductivity from the electrode to the water jacket or the atmosphere is adjustable by inserting a selected amount of insulating material 64 in the space provided. It is desired that the ignition of the combustible charge in the combustion chamber by the self-sustaining action of the compressed portion of the charge in the port or channel occur only at the higher speeds when the deposits formed cause the normal spark ignition action to fail. This is attained in part by the proper selection of the amount and type of heat insulating material.

Two ground electrodes 66 are located around the outer bottom edge of the central axial electrode 52. Electrodes 66 extend to near but do not extend across 'the open bottom end 54 of electrode 52 and so permit free access of the combustible mixture of fuel and air into the port or cavity 63. More than two grounded electrodes 66 may be used. Instead of using separate electrodes 66, the grounded electrode may take the form of a ring secured at its outer periphery to the bottom of metal shell 20 and having its inner diameter greater than the diameter of the central electrode 52 to space the ring from the central electrode a distance corresponding to the desired arcing distance of the particular ignition voltage supply.

In Fig. 8 there is shown a different form or construction using a hollow central electrode 52 like that in Fig. 6. The solid cylinder 60 is moved and adjusted in electrode 52 to obtain the desired length of port 63 and the upper end of electrode 52 is then crimped or pushed in as at 68 to seal around the upper end of rod 62 and hold piston 60 rigidly in position. The upper end of central electrode is indicated at 70. In this form of the invention the piston 60 is not adjustable after electrode 52 is crimped in position. In a further modification (not shown) the rod 62 or the space between crimping 68 and cylinder 60 is provided with highly expansible material to cause pushing down of cylinder 60 at higher temperature to automatically reduce the length of port 63 and hence the L/D at high temperatures.

The spark plug of the present invention is especially adapted for use in the present day 4-stroke internal combustion engines. For a certain speed range for an eight cylinder engine, for example, eight spark plugs each modified to have a certain L/D port or well provided in it. In any one engine the port or wells in the spark plugs will have the same L/ D ratio.

Where it is desired to provide supplementary ignition according to this invention a spark plug having a well or port of about 1 inch long and a diameter of about /8 inch is provided for use in the conventional internal combustion engines of automobiles.

The temperature and pressure developed in each combustion chamber will be transmitted to the wells or ports in the spark plugs and so the temperature and pressure in the wells or ports in the porcelain body 12 will be about the same as in the combustion chambers.

Assuming a single port 32, as the compression stroke of the engine is substantially nearing completion, a portion of the gasoline-air mixture or charge has been forced into well or port 32 in the spark plug associated with the compression stroke. These conditions are suitable for causing self-ignition of the portion of the gasolineair mixturein the well or port 32. If the regular electrical ignition fails at this instant, the supplementary ignition provided by the well or port 32 ignites the compressed charge in the combustion chamber. This action takes place in all the combustion chambers of the engine so that at the operating speed given or at slightly higher speeds, the port or well 32 forms a small compression chamber to supply supplementary ignition of the gasoline-air mixture or charge in the combustion chambers during operation of the engine, which supplementary ignition is supplied in addition to or in place of the regular electrical ignition system. That is, if the electrical ignition system fails and the spark plugs give no electric spark, or if the spark plugs occasionally misfire, the

supplementary ignition acts to supply ignition to the compressed gasoline-air mixture.

What is claimed is:

1. A spark plug including a central vertical electrode and bottom electrode means spaced from said vertical electrode to form a spark gap, said vertical electrode being formed as a hollow cylinder, a solid cylinder movably mounted in said hollow cylinder and means for adjusting the position of said solid cylinder in said hollow cylinder to adjust the length of the well formed between the bottom of said solid cylinder and the bottom portion of said hollow cylinder, said well being open at its end adjacent said spark gap.

2.. A spark plug according to claim 1 wherein said adjusting means includes an externally threaded cylinder received in the upper portion of said hollow cylinder.

3. A spark plug including a central vertical electrode and bottom electrode means spaced from said vertical electrode to form a spark gap, said vertical electrode being formed as a hollow cylinder, a solid cylinder provided with a rigid rod extending upwardly therefrom, said solid cylinder being held in position by a crimped upper portion of said hollow cylinder around said rigid rod and below the top of said hollow cylinder.

4. A spark plug including (1) a core member of electrically non-conductive material, (2) a shell member of electrically conductive material enclosing at least part of said core member, (3) a central vertical electrode extending downwardly through said core member and having a lower end therebelow, and (4) bottom electrode means extending from said shell member into spaced relation to said lower end of said central vertical electrode to form a spark gap therewith, said spark plug being characterized by at least one full bore well extending substantially vertically in said core member, and having a closed upper end, an open lower end, and a ratio of length to diameter of between 5 and 20, and said open lower end of said well being within a distance from the lower end of said central vertical electrode substantially equal to the spacing of said bottom electrode means therefrom.

5. A spark plug according to claim 4 in which said full bore Well has a length of between A5 inch and 2 inches and a diameter of between inch and inch.

6. A spark plug including (1) a core member of electrically non-conductive material, (2) a shell member of electrically conductive material enclosing at least part of said core member, (3) a central vertical electrode extending downwardly through said core member and having a lower end therebelow, and (4) bottom electrode means extending from said shell member into spaced relation to said lower end of said central vertical electrode to form a spark gap therewith, said spark plug being characterized by at least one full bore well extending substantially vertically in said core member and having a closed upper end, an open lower end, and a ratio of length to diameter of about 8, and said open 7 lower end of said well being Within a distance from the lower end of said central vertical electrode substantially equal to the spacing of said bot-tom electrode means therefrom.

7. A spark plug according to claim 6 in which said 1,941,279

full bore well has a length of about 1 inch.

References Cited in the file 0t patent UNITED STATES PATENTS 700,147 Mez ger May 13, 1902 Sharpnack Dec. 26, 1933 2,608,186 VHudson Aug. 26, 1952 

